OFDM Channel Estimation Algorithm Based On Transform Domain Processing

Orthogonal Frequency Division Multiplexing(OFDM)can be seen as a multi-carrier modulation technique improved,since the OFDM technology has a very strong resistance to multipath fading and high spectrum efficiency.So OFDM has been regarded as the most important one of the key technologies in the fourth generation mobile communication system.In this paper,the channel estimation algorithm uses the pilot structure based on the comb pilot.To solve the problem that the channel estimation algorithm combines wavelet de-noising with interpolation in DFT does not eliminate the noise in the cyclic prefix length,a new algorithm of channel estimation is proposed,which is the combination of algorithm wavelet de-noising and improved DFT interpolation.This channel estimation algorithm first uses the discrete wavelet transform of least squares(LS)method to estimate the results of threshold de-noising processing,and set the corresponding threshold in the process of DFT interpolation based on cyclic prefix inside and outside the noise's variance of the mean,then handle the noise of the cyclic prefix length again to reduce the further influence of noise.The simulation results shows that under the unchanged premise of complexity the improved algorithm can remove the influence of noise better,and improved the accuracy of channel estimation.But based on DFT interpolation channel estimation algorithm has better performance on condition that the channel delay must be an integer multiple of the sampling period.Otherwise,the signal will produce a spectrum of energy leakage.Compared with interpolation DFT,DCT transform coefficient data series do after the resulting energy will exhibit more concentrated,so can more effectively inhibit the spectral energy leak.Therefore,this paper also has studied based DCT interpolation channel estimation algorithm,and a new algorithm of channel estimation is proposed,the algorithm combines wavelet de-noising with improved DCT.First the algorithm of least squares(LS)method to estimate the results of wavelet threshold de-noising,in order to eliminate the influence of noise then DCT interpolation.The simulation results shows that under the unchanged premise of complexity the algorithm is better than the based on DFT interpolation channel estimation algorithm.